In recent years, in order to save paper resources, image recording apparatus which can record images on both sides of a sheet of paper (a recording medium) have been used in increasing numbers of offices and homes.
An increasing number of image recording apparatuses of this kind are developed in various types. For example, U.S. Pat. No. 6,975,814 (Japanese Patent Laid-open Publication No. 2004-102165 (FIG. 2)) discloses an image recording apparatus of this kind. A feed cassette is set (arranged) in the bottom of the main case of this image recording apparatus, and an electrophotographic toner type image recording unit is arranged over the feed cassette in the main case. In this image recording apparatus, a sheet of paper is transported from the feed cassette through a U-shaped transporting (conveying) passage in an upward direction toward the recording unit, where an image is first recorded on one side of the sheet. Subsequently, the sheet is transported through a fixing device to a discharge passage, where the upstream end of the sheet is nipped by a pair of discharge rollers, which is arranged at the end of the discharge passage which is downstream in the transporting direction. The sheet is stopped once with its upstream end nipped. Subsequently, the sheet is turned from the discharge passage and transported backward toward a reverse transporting passage, which extends over the feed cassette. As a result, the sheet is returned in an upside-down state to the U-shaped transporting passage. This makes it possible to record an image on the still blank side of the sheet at the recording unit, which is downstream from the U-shaped transporting passage.
An ink jet printer provided with an ink jet image recording unit (an ink jet head) is known as another image recording apparatus which can record images on both sides of a recording medium. The ink jet printer prints images on both sides of a sheet of paper as follows. First, while a pair of feed rollers and a pair of discharge rollers are feeding the sheet downstream below the ink jet head, the head prints an image on one side of the sheet. Subsequently, a discharge roller of the pair of discharge rollers is rotated reversely to return the sheet upstream below (passing through a portion below) the ink jet head. The returned sheet is transported through a predetermined transporting passage to be turned upside down so that the blank (back) side of the sheet can face the ink jet head. Then, while the two roller pairs are feeding the turned sheet again downstream below (passing through the portion below) the ink jet head, the head prints an image on the back side of the sheet.
As is the case with the image recording apparatus disclosed in U.S. Pat. No. 6,975,814, the ink jet printer is provided with a reverse transporting unit which reverses the transporting direction at a position in a discharge transporting passage after an image is recorded on one side of a sheet of paper. This increases the number of parts of the image recording apparatus, complicates its structure greatly and makes the apparatus bulky. The image recording apparatus has a long reverse transporting passage. While a sheet of paper with an image recorded on its one side is transported through the reverse transporting passage, this side is in contact with a transporting roller etc. and may consequently be stained with ink. Each of the foregoing ink jet image recording apparatuses, which can record images on both sides of a sheet of paper, also has a transporting path for sheet reversal. This makes the image recording apparatuses large in size and complicated in structure.